The present invention concerns a process for the preparation of 1, 1, 2, 2 - tetrahydro fluorinated alkanols and of the carboxylic acid esters of these alkanols. These products have the following general formulae: EQU R.sub.F CH.sub.2 CH.sub.2 OH and EQU R.sub.F CH.sub.2 CH.sub.2 OCOR.sup.1
in which R.sub.F represents a straight of branched chain perfluorinated radical containing from 1 to 20 carbon atoms and R.sup.1 represents a hydrogen atom or an aliphatic or aromatic hydrocarbon radical.
Up to the present time, these products have been obtained according to the process described in French Pat. No. 1,380,579, by a reaction of the iodides, R.sub.F CH.sub.2 CH.sub.2 I, with fuming sulfuric acid, followed by a hydrolysis of the sulfates having been formed. However, this process presents the disadvantages of furnishing large quantities of sulfuric diesters which are difficult to hydrolyze. According to the process described in U.S. Pat. No. 3,239,557, it is possible to obtain the esters R.sub.F C.sub.2 H.sub.4 OCOR.sup.1 by the conventional reaction of the iodides R.sub.F C.sub.2 H.sub.4 I with salts of the carboxylic acids R.sup.1 COOH. The yields, however, are not very good, since larger or smaller quantities of olefins R.sub.F CH.dbd.CH.sub.2 are formed.
The alcohols can also be obtained according to the process of French Pat. No. 2,096,179, which consists of preparing the nitrates R.sub.F CH.sub.2 CH.sub.2 ONO.sub.2 by the reaction of the iodides R.sub.F CH.sub.2 CH.sub.2 I with nitric acid and of hydrogenating these nitrates in alcohol. This process, however, presents the drawback of necessitating two reaction stages, the last one of which must be carried out under a high hydrogen pressure.
French Pat. No. 2,180,113 describes a process for the production of mixtures of alcohol R.sub.F C.sub.2 H.sub.4 OH and of formates R.sub.F C.sub.2 H.sub.4 OCOH by the reaction, at high temperture, of iodides R.sub.F C.sub.2 H.sub.4 I with dimethyl formamide in the presence of a little bit of water. This process has the drawback of requiring very strict reaction conditions and of furnishing some olefin R.sub.F CH.dbd.CH.sub.2 as a by-product which diminishes the yield accordingly. A good selectivity in alcohol and formate can only be obtained by using very large quantities of dimethyl formamide.